Support dynamic price_suffix in in-app marketplace

[andfinally]

All Submissions:

• Have you followed the WooCommerce Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Adds support for a price_suffix property in each product in the WooCommerce.com search and featured endpoints, which provide the data for the product cards in the in-app marketplace. This will allow us to list products whose fees are per month.

How to test the changes in this Pull Request:

Note for GlobalStep testers

The required data changes for this PR haven't been implemented on WooCommerce.com yet, and the test below requires using the test data in a GitHub gist. For now, it's fine if we simply continue to see "per year" on the prices of products in the Marketplace, for example $29.00 per year, where the product is not free.

Test using dummy data

1. Check out this branch.
2. Edit wp-content/plugins/woocommerce/plugins/woocommerce/includes/admin/class-wc-admin-addons.php:143 to point to this gist with test data: https://gist.githubusercontent.com/andfinally/84015c40afc8dc628f2496c9c4faf0f8/raw/search.json.

$raw_extensions = wp_safe_remote_get(
	'https://gist.githubusercontent.com/andfinally/84015c40afc8dc628f2496c9c4faf0f8/raw/search.json',
	array( 'headers' => $headers )
);

3. Go to wp-admin/admin.php?page=wc-addons&section=payment-gateways.
4. Check that Authorize.Net has a price "per month".

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

Changelog entry

Add - Support for dynamic price period in in-app marketplace product cards.

FOR PR REVIEWER ONLY:

• I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.

[barryhughes]

Just need a minor tweak to satisfy linting rules 👍

[barryhughes]

LGTM!

(Triggered a re-run of a couple of checks, however the failures were likely unrelated to this change.)

[github-actions]

Hi @barryhughes, thanks for merging this pull request. Please take a look at these follow-up tasks you may need to perform:

• Add the status: needs changelog label
• Add the status: needs testing instructions label

[andfinally]

Great! Thanks for the review Barry.